At the wireless base station for performing communications by using an adaptive array antenna, the adaptive array antenna has different effects based on arrangements of antenna elements. When the antenna elements of the adaptive array antenna are arranged at short intervals, antenna correlation becomes high, which enables to handle fluctuations of fading. In contrast, when the antenna elements of the adaptive array antenna are arranged at long intervals, the antenna correlation becomes low, which promises a high diversity effect.
Accordingly, in order to enhance the diversity effect, the wireless base station arranges the antenna elements at several wavelength intervals (group A) in consideration of the antenna correlation stated above. However, since the antenna elements are arranged at long intervals, this wireless base station has a problem that it is difficult to control directivity to separate transmission waves (desired waves) transmitted from a terminal A and transmission waves (interference waves) transmitted from a terminal B. In order to address such problem, there is suggested an antenna device of a wireless base station which has antenna elements (group B) arranged at wavelength intervals different from those of a group A and, if it is not possible to perform a desired directivity control, changes directivity characteristics by switching from any of antennas in the group A being used to any of the antenna elements in the group B in order to separate the desired waves from the interference waves (see Patent Document 1).
In addition, a wireless communication system including an adaptive array wireless base station having a plurality of antenna elements and a mobile communication terminal may have a problem that at reception throughput is deteriorated in some conditions of a user of the terminal performing wireless communications with the wireless base station. For example, if the user is using the terminal while moving at a speed equal to or faster than 80 km/h, it causes fast fading variation in reception signals, which deteriorates throughput.
In order to obtain better throughput, there is suggested a wireless communication apparatus which selects transmission by the adaptive array antenna or transmission by MIMO, based on reception quality information obtained from a communication terminal of a counterpart (see Patent Document 2).